Compound change gear transmissions of the type having one or more auxiliary sections connected in series with a main transmission section are known in the prior art. Briefly, by utilizing main and auxiliary transmission sections connected in series, assuming proper sizing of the ratio steps, the total of available transmission ratios is equal to the product of the main and auxiliary section ratios. By way of example, a compound change gear transmission comprising a four (4) speed main section connected in series with a three (3) speed auxiliary section will theoretically provide twelve (4.times.3=12) available ratios.
Auxiliary transmission sections are of three general types: range type, splitter type or combined range/splitter type. In compound transmissions having a range type auxiliary section, the ratio step or steps are greater than the total ratio coverage of the main transmission section and the main section is shifted progressively through its ratios in each range. Examples of compound transmissions having range type auxiliary sections may be seen by reference to U.S. Pat. No. 3,105,395; U.S. Pat. No. 2,637,222; and U.S. Pat. No. 2,637,221, the disclosures of which are hereby incorporated by reference.
In compound transmissions having a splitter type auxiliary section, the ratio steps of the splitter auxiliary section are less than the ratio steps of the main transmission section and each main section ratio is split, or subdivided, by the splitter section. Examples of compound change gear transmissions having splitter type auxiliary sections may be seen by reference to U.S. Pat. No. 4,290,515; U.S. Pat. No. 3,799,002; U.S. Pat. No. 4,440,037; and U.S. Pat. No. 4,527,447, the disclosures of which are hereby incorporated by reference.
In a combined range and splitter type auxiliary section, or sections, both range and splitter type ratios are provided allowing the main section to be progressively shifted through its ratios in at least two ranges and also allowing the main section ratios to be split in at least one range. Examples of a compound transmission having a single combined range/splitter type auxiliary section may be seen by reference to U.S. Pat. No. 3,283,613 and U.S. Pat. No. 3,648,546, the disclosures of which are hereby incorporated by reference. Eaton also produces the "Super 10" compound transmission which has a 2+1 main section and an auxiliary section having both range and splitter gears. All three forward ratios are used in the low range, while two forward ratios are repeated in the high range. This results in a standard 5 speed shift pattern. Another example of a combined range and splitter type compound transmission is the "Ecosplit" model of transmission sold by Zahnradfabrik Friedrichshafen Aktiengeseushaft of Friedrichshafen, Germany, which utilizes a separate splitter auxiliary section in front of, and a separate range auxiliary section behind, the main transmission section. Still another example is the RM0-13-145A thirteen speed transmission sold by Rockwell Corporation, in which the high range forward ratios are split.
Splitter shift systems may be either synchronized on non-synchronized. Conventional synchronizing systems, including those on compound transmissions having head end mounted splitters, use high force actuators which typically develop 500-600 pounds of force to effect the splitter shift. Furthermore, these synchronized systems generally also require that the master clutch be disengaged on all splits, and employ costly master clutch interlocks in the case of head end mounted splitters. While nonsynchronized splitter clutching systems on either front or rear end splitters use lower force actuators, the resulting splitter shifts are often neither smooth nor jerkless.